This invention relates to a cooling apparatus for cooling a carbon brick in the sidewall of a blast furnace bottom.
The service life of a blast furnace bottom determines that of an entire blast furnace, and the prevention of wear of carbon bricks forming the sidewall of a blast furnace bottom is the most important task for extending the service life of the blast furnace. Erosion by molten iron, embrittlement resulting from thermal stress, etc. are responsible for the wear of the carbon bricks in the sidewall of the furnace bottom, and intensive cooling is considered to be the most effective measure to prevent the carbon bricks from wearing.
Carbon bricks, which are highly resistant against molten iron and excellent in heat conductivity, are used as refractory bricks for the sidewall of a conventional blast furnace bottom for preventing the erosion by the molten iron. The carbon bricks are cooled by water spray on the outer steel shell of the furnace bottom or stave coolers embedded in the furnace bottom sidewall. Whereas the carbon bricks are cooled indirectly from outside by the water spray method on the shell, they are cooled more directly, and from a closer position, by the stave cooler method.
FIG. 4 shows a conventional brick cooling structure using stave coolers 11. The stave coolers 11 are embedded between the carbon bricks 1 and the steel shell 13, and ramming material 12 fills the space between the stave coolers 11 and the bricks 1 to absorb positioning error in the installation of the stave coolers 11 and the shifting of the carbon bricks 1 owing to their thermal expansion.
The ramming material 12 consists of a highly heat conductive and elastic material and, when the carbon brick 1 thermally expands after the blow-in of the blast furnace, expansion is absorbed by the compression of the ramming material 12 and gaps are prevented from forming around the stave coolers 11, and their cooling ability is thus maintained.
However, the ramming material 12 deteriorates and the carbon bricks 1 expand and contract over the operation period of a blast furnace, and gaps may form between the carbon bricks 1 and the stave coolers 11, causing the deterioration of the cooling ability. When, for instance, some deposit forms on the inner surfaces of the carbon bricks 1, the cooling from the side of the stave coolers 11 becomes too large at the portion and the brick temperature falls. The carbon bricks 1 contract as a result but, since the ramming material 12 does not expand, gaps form locally between the carbon bricks 1 and the stave coolers 11, causing the cooling ability to fall.
As a countermeasure against the above fall of the cooling ability, Japanese Unexamined Patent Publication No. H10-280017 proposes a method, of repairing the sidewall of a blast furnace bottom, wherein the heat conduction of the ramming material 12 is measured, a steel shell 13 is cut out at the portion where the heat conduction is low on an occasion of temporary shutdown of the furnace, the ramming material 12 is removed from the portion and replaced with a new ramming material 12, and the blowing is resumed after restoring the steel shell 13.
By conventional cooling methods using the stave coolers 11, the carbon bricks 1 are eroded at the parts contacting the molten iron, leading to the loss of the bricks when gaps form between the carbon bricks 1 and the stave coolers 11 owing to the expansion and contraction of the carbon bricks 1 and the deterioration of the ramming material 12 and, as explained above, the cooling ability is lowered as a result. To forestall the problem, the blast furnace is blown-off before the bricks are lost and repair work is done to replace the bricks.
The repair work as proposed in said patent publication is done for the purpose of extending the service life of a blast furnace as much as possible. However, said repair work is only a temporary measure taken after the fall of the cooling ability has actually taken place, and the erosion of the carbon bricks by the molten iron continues as a result of the reduced cooling ability.
Further, Japanese Unexamined Patent Publication No. H7-133989 proposes a method wherein, during carbon brick laying work of a blast furnace, several carbon bricks are bonded together with a carbon adhesive to form a large block. An adhesive consisting of carbon powder, a liquid synthetic resin and a hardening agent is disclosed as the adhesive used therein.
The object of the present invention is to suppress the erosion of carbon bricks by molten iron by preventing the ability to cool the carbon bricks from falling at the sidewall of a blast furnace bottom, and thereby to extend the service life of the blast furnace.
The present invention relates to a cooling apparatus for a brick in a sidewall of a blast furnace bottom, which comprises a carbon brick forming a sidewall of a blast furnace bottom, a metal cooler cooling the carbon brick, and a bonding layer bonding the carbon brick and the metal cooler, wherein the bonding layer contains 50 mass % or more, preferably 50 to 85 mass %, of solid carbon as a result of an adhesive, containing carbon powder, a synthetic resin and a hardening agent, forming the bonding layer.
In the cooling apparatus for a brick in a sidewall of a blast furnace bottom according to the present invention, it is preferable that the apparatus further comprises: anchor bolts each of which having one end embedded in an outer surface of the carbon brick and the other end piercing the bonding layer and the cooler and extending beyond the outer surface of the cooler, lock nuts fastening the cooler and the brick at the other end of the anchor bolts, and washers having a spring function provided between the lock nuts and the cooler.